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  • How to Boost Web Site Traffic With SEO

    SEO is important if you'd like to get your internet site listed at the very top of the search engine positions. You'll have to design and write your pages not only for the client, but also for the search site spiders and crawlers.

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  • Boost Mersenne Twister: how to seed with more than one value?

    - by Eamon Nerbonne
    I'm using the boost mt19937 implementation for a simulation. The simulation needs to be reproducible, and that means storing and potentially reusing the RNG seeds later. I'm using the windows crypto api to generate the seed values because I need an external source for the seeds and not because of any particular guarantees of randomness. The output of any simulation run will have a note including the RNG seed - so the seed needs to be reasonably short. On the other hand, as part of the analysis of the simulation, I'll be comparing several runs - but to be sure that these runs are actually different, I'll need to use different seeds - so the seed needs to be long enough to avoid accidental collisions. I've determined that 64-bits of seeding should suffice; the chance of a collision will reach 50% after about 2^32 runs - that probability is low enough that the average error caused by it is negligible to me. Using just 32-bits of seed is tricky; the chance of a collision reaches 50% already after 2^16 runs; and that's a little too likely for my tastes. Unfortunately, the boost implementation either seeds with a full state vector - which is far, far too long - or a single 32-bit unsigned long - which isn't ideal. How can I seed the generator with more than 32-bits but less than a full state vector? I tried just padding the vector or repeating the seeds to fill the state vector, but even a cursory glance at the results shows that that generates poor results.

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  • Is there a Boost (or other common lib) type for matrices with string keys?

    - by mohawkjohn
    I have a dense matrix where the indices correspond to genes. While gene identifiers are often integers, they are not contiguous integers. They could be strings instead, too. I suppose I could use a boost sparse matrix of some sort with integer keys, and it wouldn't matter if they're contiguous. Or would this still occupy a great deal of space, particularly if some genes have identifiers that are nine digits? Further, I am concerned that sparse storage is not appropriate, since this is an all-by-all matrix (there will be a distance in each and every cell, provided the gene exists). I'm unlikely to need to perform any matrix operations (e.g., matrix multiplication). I will need to pull vectors out of the matrix (slices). It seems like the best type of matrix would be keyed by a Boost unordered_map (a hash map), or perhaps even simply an STL map. Am I looking at this the wrong way? Do I really need to roll my own? I thought I saw such a class somewhere before. Thanks!

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  • Compiling my Boost/NTL program with c++ on Linux.

    - by Martin Lauridsen
    Hi SO, I wrote a client program and a server program, that uses the NTL library and Boost::Asio, to do client/server communication for an integer factorization application, in C++. Both sides consist of several headers and cpp files. Both project compile fine individually on Windows in Visual Studio. All I did, was add the include path of NTL and Boost to both projects: Additional include paths: "D:\Downloads\WinNTL-5_5_2\include";D:\boost_1_42_0 Furthermore, for both projects, I added the two library paths to both projects in VS: Additional library directories: D:\boost_1_42_0\stage\lib;"D:\Documents\Visual Studio 2008\Projects\ntl\Debug" And added under Additional dependencies: ntl.lib As said, it compiles fine on Windows. But when I put the code on a Linux machine provided by university, I try to compile with the following statement c++ -I/appl/htopopt/Linux_x86_64/NTL-5.4.2/include -I/appl/htopopt/Linux_x86_64/boost_1_43_0/include client_protocol.cpp mpqs_client.cpp mpqs_sieve.cpp mpqs_helper.cpp -o mpqs_helper -L/appl/htopopt/Linux_x86_64/NTL-5.4.2/lib -lntl -L/appl/htopopt/Linux_x86_64/gmp-4.2.1/lib -lgmp -lm -L/appl/htopopt/Linux_x86_64/boost_1_43_0/lib -lboost_system -static Upon doing this, I get a huuuge error, which I posted here. Any idea how to fix this, please??

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  • (How) Can I approximate a "dynamic" index (key extractor) for Boost MultiIndex?

    - by Sarah
    I have a MultiIndex container of boost::shared_ptrs to members of class Host. These members contain private arrays bool infections[NUM_SEROTYPES] revealing Hosts' infection statuses with respect to each of 1,...,NUM_SEROTYPES serotypes. I want to be able to determine at any time in the simulation the number of people infected with a given serotype, but I'm not sure how: Ideally, Boost MultiIndex would allow me to sort, for example, by Host::isInfected( int s ), where s is the serotype of interest. From what I understand, MultiIndex key extractors aren't allowed to take arguments. An alternative would be to define an index for each serotype, but I don't see how to write the MultiIndex container typedef ... in such an extensible way. I will be changing the number of serotypes between simulations. (Do experienced programmers think this should be possible? I'll attempt it if so.) There are 2^(NUM_SEROTYPES) possible infection statuses. For small numbers of serotypes, I could use a single index based on this number (or a binary string) and come up with some mapping from this key to actual infection status. Counting is still darn slow. I could maintain a separate structure counting the total numbers of infecteds with each serotype. The synchrony is a bit of a pain, but the memory is fine. I would prefer a slicker option, since I would like to do further sorts on other host attributes (e.g., after counting the number infected with serotype s, count the number of those infected who are also in a particular household and have a particular age). Thanks in advance.

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  • Compact representation of GUID/UUID?

    - by chakrit
    I need to generate a GUID and save it via a string representation. The string representation should be as short as possible as it will be used as part of an already-long URL string. Right now, instead of using the normal abcd-efgh-... representation, I use the raw bytes generated and base64-encode them instead, which results in a somewhat shorter string. But is it possible to make it even shorter? I'm OK with losing some degree of uniqueness and keeping a counter, but scanning all existing keys is not an option. Suggestions?

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  • UUID Cassandra.

    - by Sandeep
    Hi all, I am new to Cassandra. I am trying to insert some values to the columnfamily. The definition of columnfamily in the config file is as follows. <ColumnFamily Name="CommandQueue" ColumnType="Super" CompareWith="TimeUUIDType" CompareSubcolumnsWith="UTF8Type"/> When ever I try to insert values to I always get "InvalidRequestException(why: UUIDs must be exactly 16 bytes)". I am using batch_mutate() to insert column. How can I insert values to the column family.

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  • PHP/MySQL: Storing and retrieving UUIDS

    - by Greg
    I'm trying to add UUIDs to a couple of tables, but I'm not sure what the best way to store/retrieve these would be. I understand it's far more efficient to use BINARY(16) instead of VARCHAR(36). After doing a bit of research, I also found that you can convert a UUID string to binary with: UNHEX(REPLACE(UUID(),'-','')) Pardon my ignorance, but is there an easy way to this with PHP and then turn it back to a string, when needed, for readability? Also, would it make much difference if I used this as a primary key instead of auto_increment? EDIT: Found part of the answer: $bin = pack("h*", str_replace('-', '', $guid)); How would you unpack it?

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  • "Expected initializer before '<' token" in header file

    - by Sarah
    I'm pretty new to programming and am generally confused by header files and includes. I would like help with an immediate compile problem and would appreciate general suggestions about cleaner, safer, slicker ways to write my code. I'm currently repackaging a lot of code that used to be in main() into a Simulation class. I'm getting a compile error with the header file for this class. I'm compiling with gcc version 4.2.1. // Simulation.h #ifndef SIMULATION_H #define SIMULATION_H #include <cstdlib> #include <iostream> #include <cmath> #include <string> #include <fstream> #include <set> #include <boost/multi_index_container.hpp> #include <boost/multi_index/hashed_index.hpp> #include <boost/multi_index/member.hpp> #include <boost/multi_index/ordered_index.hpp> #include <boost/multi_index/mem_fun.hpp> #include <boost/multi_index/composite_key.hpp> #include <boost/shared_ptr.hpp> #include <boost/tuple/tuple_comparison.hpp> #include <boost/tuple/tuple_io.hpp> #include "Parameters.h" #include "Host.h" #include "rng.h" #include "Event.h" #include "Rdraws.h" typedef multi_index_container< // line 33 - first error boost::shared_ptr< Host >, indexed_by< hashed_unique< const_mem_fun<Host,int,&Host::getID> >, // 0 - ID index ordered_non_unique< tag<age>,const_mem_fun<Host,int,&Host::getAgeInY> >, // 1 - Age index hashed_non_unique< tag<household>,const_mem_fun<Host,int,&Host::getHousehold> >, // 2 - Household index ordered_non_unique< // 3 - Eligible by age & household tag<aeh>, composite_key< Host, const_mem_fun<Host,int,&Host::getAgeInY>, const_mem_fun<Host,bool,&Host::isEligible>, const_mem_fun<Host,int,&Host::getHousehold> > >, ordered_non_unique< // 4 - Eligible by household (all single adults) tag<eh>, composite_key< Host, const_mem_fun<Host,bool,&Host::isEligible>, const_mem_fun<Host,int,&Host::getHousehold> > >, ordered_non_unique< // 5 - Household & age tag<ah>, composite_key< Host, const_mem_fun<Host,int,&Host::getHousehold>, const_mem_fun<Host,int,&Host::getAgeInY> > > > // end indexed_by > HostContainer; typedef std::set<int> HHSet; class Simulation { public: Simulation( int sid ); ~Simulation(); // MEMBER FUNCTION PROTOTYPES void runDemSim( void ); void runEpidSim( void ); void ageHost( int id ); int calcPartnerAge( int a ); void executeEvent( Event & te ); void killHost( int id ); void pairHost( int id ); void partner2Hosts( int id1, int id2 ); void fledgeHost( int id ); void birthHost( int id ); void calcSI( void ); double beta_ij_h( int ai, int aj, int s ); double beta_ij_nh( int ai, int aj, int s ); private: // SIMULATION OBJECTS double t; double outputStrobe; int idCtr; int hholdCtr; int simID; RNG rgen; HostContainer allHosts; // shared_ptr to Hosts - line 102 - second error HHSet allHouseholds; int numInfecteds[ INIT_NUM_AGE_CATS ][ INIT_NUM_STYPES ]; EventPQ currentEvents; // STREAM MANAGEMENT void writeOutput(); void initOutput(); void closeOutput(); std::ofstream ageDistStream; std::ofstream ageDistTStream; std::ofstream hhDistStream; std::ofstream hhDistTStream; std::string ageDistFile; std::string ageDistTFile; std::string hhDistFile; std::string hhDistTFile; }; #endif I'm hoping the other files aren't so relevant to this problem. When I compile with g++ -g -o -c a.out -I /Applications/boost_1_42_0/ Host.cpp Simulation.cpp rng.cpp main.cpp Rdraws.cpp I get Simulation.h:33: error: expected initializer before '<' token Simulation.h:102: error: 'HostContainer' does not name a type and then a bunch of other errors related to not recognizing the HostContainer. It seems like I have all the right Boost #includes for the HostContainer to be understood. What else could be going wrong? I would appreciate immediate suggestions, troubleshooting tips, and other advice about my code. My plan is to create a "HostContainer.h" file that includes the typedef and structs that define its tags, similar to what I'm doing in "Event.h" for the EventPQ container. I'm assuming this is legal and good form.

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  • Portable C++ library for IPC (processes and shared memory), Boost vs ACE vs Poco?

    - by user363778
    Hi, I need a portable C++ library for doing IPC. I used fork() and SysV shared memory until now but this limits me to Linux/Unix. I found out that there are 3 major C++ libraries that offer a portable solution (including Windows and Mac OS X). I really like Boost, and would like to use it but I need processes and it seems like that this is only an experimental branch until now!? I have never heard of ACE or POCO before and thus I am stuck I do not know which one to choose. I need fork(), sleep() (usleep() would be great) and shared memory of course. Performance and documentation are also important criteria. Thanks, for your Help!

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  • Using boost.python to import a method with opencv calls but failing due to symbols not being found a

    - by nmz787
    So I don't have the code right now, as I am not home... but i used the boost library for python in C++ to allow python to access a function called something like loadImageIntoMainWindow(string filepath) in the C++ source code the method calls opencv methods that are imported at the top of the file, I included opencv in my Jamroot file, and also found a way to compile and link manually on the command line... in either case when I run my python file it complains that the symbols aren't found for the first function call to an opencv method... I will update as soon as I get home with the C++, the command line compilation lines, the Jamroot, and the python files

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